1. Field of the Invention
The present invention relates to a composition having an effect of improving cerebration. More specifically, the present invention relates to a cerebration improver effective for the prophylaxis and treatment of Parkinson's disease and dementia such as Alzheimer's disease.
2. Description of the Related Art
A. Bruni, et al. report that the brain glucose level in mice injected via the caudal vein with phosphatidylserine extracted from bovine brain is increased by about 4 fold the level in the control group (A. Bruni et al., Nature, Vol. 260, p. 331, 1976).
A. Zanotti et al. also report that the oral administration of phosphatidylserine extracted from bovine brain to aged rats with memory deficits for 12 weeks improved the performance of the aged rats (A. Zanotti et al., Psychopharmacology Berl., Vol. 99, P. 316, 1989).
Furthermore, it is confirmed at a double-blind placebo-controlled clinical trial for humans the efficacy of phosphatidylserine extracted from bovine brain in improving the memory impairment in Alzheimer's disease and during the aging stage (P. J. Delwaide et al., Acta Neurol. Scand., Vol. 73, p. 136, 1986; R. R. Engel et al., Eur. Neuropsychopharmacol., Vol. 2, p. 149, 1992; T. Cenacci et al., Aging Clin. Exp. Res., Vol. 5, p. 123, 1993).
As has been described above, bovine brain-derived phosphatidylserine having the effect of increasing brain glucose level has an effect of improving the cerebration in rats and humans. Therefore, it is indicated that the degree of the increase in brain glucose level is an important indicator for selecting a substance with the action of improving cerebration. However, it is reported in the paper of A. Bruni et al. that the phosphatidylserine extracted from soy bean does not have such action. Hence, it is generally believed that the fatty acid composition of phosphatidylserine is a significant factor for exerting the action of improving cerebration.
More specifically, phosphatidylserine extracted from bovine brain has a highly characteristic fatty acid composition such that the structural fatty acid chain thereof contains higher levels of stearic acid chain at position .alpha. and oleic acid chain at position .beta.. Generally, it has been believed currently that the specific structural fatty acid chain is essential for the expression of the action of improving cerebration.
Alternatively, Japanese Patent Laid-open No. 6-279311 describes that phosphatidylserine of a type with a synthesized specific fatty acid chain is promising for use in the treatment of senile dementia on the basis of its action activating protein kinase C-isozyme, but the efficacy has not yet been confirmed in vivo.
As to phosphatidylserine of the lyso type, lysophosphatidyl-L-serine derived from bovine brain-derived phosphatidylserine has an action for increasing the level of brain glucose and/or blood glucose (H. W. Chang et al., Br. J. Pharmacol., Vol. 93, p. 647, 1988).
Thus, it has been believed that phosphatidylserine extracted from bovine brain has an action of increasing brain glucose level owing to the specific fatty acid composition.
As has been mentioned above, conventionally known references have indicated that only phosphatidylserine extracted from bovine brain or lysophosphatidylserine has the action of increasing brain glucose level. However, it is with no doubt that phosphatidylserine extracted from bovine brain has severe limits from the respect of cost and supply scale because only about 1 g of phosphatidylserine can be available from the brain of a cow.